THE.   LETTER     OF 
P       E       T       R       U       S 

PEREGRINUS 

ON    THE    MAGNET,   A,D.    1269 


LETTER  OF 

PETRUS  PEREGRINUS 

ON  THE  MAGNET 

A.D.   1269 


THE     LETTER     OF 
P      E      T      R      U      S 

PEREGRINUS 

ON    THE    MAGNET,    A.D.    1269 

TRANSLATED  BY 

BROTHER    ARNOLD,    M.Sc. 

PRINCIPAL  OF  LA    SALLE    INSTITUTE,  TROY 
WITH 

INTRODUCTORY   NOTICE 

BY 

BROTHER    POTAMIAN,  D.Sc. 

PROFESSOR  OF  PHYSICS  IN    MANHATTAN 
COLLEGE,  NEW    YORK 


NEW   YORK 

McGRAW  PUBLISHING  COMPANY 
MCMIV 


Copyright,  1 904,  by 
McGRAw  PUBLISHING  COMPANY 


INTRODUCTORY 


SRLF 
URL 

5140247 


THE  magnetic  lore  of  classic  antiquity  was 
scanty  indeed,  being  limited  to  the  at- 
traction which  the  lodestone  manifests 
for  iron.     Lucretius  (99-55  B.  C.),  however,  in 
his  poetical  dissertation  on  the  magnet,  contained 
in  De  Rerum  Natura,  Book  VI.1  recognizes  mag- 
netic repulsion,  magnetic  induction,  and  to  some 
extent  the  magnetic  field  with  its  lines  of  force, 
for  in  verse  1 040  he  writes  : 

Oft  from  the  magnet,  too,  the  steel  recedes, 
Repelled  by  turns  and  re-attracted  close. 

And  in  verse  1085  : 

Its  viewless,  potent  virtues  men  surprise  ; 

Its  strange  effects,  they  view  with  wond'ring  eyes 


1  With  very  few  exceptions  all  the  works  referred  to  in  this  notice  will 
be  found  in  the  Wheeler  Collection  in  the  Library  of  the  American  In- 
stitute of  Electrical  Engineers,  New  York. 


THE    LETTER    OF   PEREGRINUS 

When  without  aid  of  hinges,  links  or  springs 

A  pendant  chain  we  hold  of  steely  rings 

Dropt  from  the  stone — the  stone  the  binding  source — 

Ring  cleaves  to  ring  and  owns  magnetic  force  : 

Those  held  above,  the  ones  below  maintain, 

Circle  'neath  circle  downward  draws  in  vain 

Whilst  free  in  air  disports  the  oscillating  chain. 

The  poet  Claudian  (365-408  A.  D.)  wrote  a 
short  idyll  on  the  attractive  virtue  of  the  lode- 
stone  and  its  symbolism  ;  St.  Augustine  (354- 
430),  in  his  work  De  Civitate  Dei,  records  the 
fact  that  a  lodestone,  held  under  a  silver  plate, 
draws  after  it  a  scrap  of  iron  lying  on  the  plate. 
Abbot  Neckam,  the  Augustinian  (1157-1217), 
distinguishes  between  the  properties  of  the  two 
ends  of  the  lodestone,  and  gives  in  his  De  Uten- 
silibus,  what  is  perhaps  the  earliest  reference  to 
the  mariner's  compass  that  we  have.  Albertus 
Magnus,  the  Dominican  (1193-1280),  in  his 
treatise,  De  Mineralibus,  enumerates  different  kinds 
of  natural  magnets  and  states  some  of  the  prop- 
erties commonly  attributed  to  them;  the  min- 
strel, Guyot  de  Provins,  in  a  famous  satirical  poem, 
written  about  I  208,  refers  to  the  directive  qual- 


INTRODUCTORY 

ity  of  the  lodestone  and  its  use  in  navigation,  as 
do  also  Cardinal  de  Vitry  in  his  Historia  Orien- 
talis  (1215-1220);  Brunetto  Latini,  poet,  orator 
and  philosopher,  in  his  Tresor  des  Sciences,  a  veri- 
table library,  written  in  Paris  in  1 260 ;  Ray- 
mond Lully,  the  Enlightened  Doctor,  in  his 
treatise,  De  Confemp/attone,  begun  in  1272,  and 
Guido  Guinicelli,  the  poet-priest  of  Bologna, 
who  died  in  i  276. 

The  authors  of  these  learned  works  were  too 
busy  with  the  pen  to  find  time  to  devote  to  the 
close  and  prolonged  study  of  natural  phenomena 
necessary  for  fruitful  discovery,  and  so  had  to  con- 
tent themselves  with  recording  and  discussing  in 
their  tomes  the  scientific  knowledge  of  their  age 
without  making  any  notable  additions  to  it. 

But  this  was  not  the  case  with  such  contem- 
poraries of  theirs  as  Roger  Bacon,  the  Francis- 
can, and  his  Gallic  friend,  Pierre  de  Maricourt, 
commonly  called  Petrus  Peregrinus,  the  subject 
of  the  present  notice,  a  man  of  academic  culture 
and  of  a  practical  rather  than  speculative  turn  of 
mind.  Of  the  early  years  of  Peregrinus  nothing 


THE   LETTER   OF   PEREGRINUS 

however,  than  the  knight  of  Foucaucourt  was 
Roger  Bacon,  who  held  Peregrinus  in  the  very 
highest  esteem,  as  the  following  glowing  testi- 
mony shows  :  "  There  are  but  two  perfect  math- 
ematicians,'* wrote  the  English  monk,  "  John  of 
London  and  Petrus  de  Maharne-Curia,  a  Picard." 
Further  on  in  his  Opus  Tertium,  Bacon  thus  ap- 
praises the  merits  of  the  Picard  :  "  I  know  of 
only  one  person  who  deserves  praise  for  his  work 
in  experimental  philosophy,  for  he  does  not  care 
for  the  discourses  of  men  and  their  wordy  war- 
fare, but  quietly  and  diligently  pursues  the  works 
of  wisdom.  Therefore,  what  others  grope  after 
blindly,  as  bats  in  the  evening  twilight,  this  man 
contemplates  in  all  their  brilliancy  because  he  is 
a  master  of  experiment.  Hence,  he  knows  all 
natural  science  whether  pertaining  to  medicine 
and  alchemy,  or  to  matters  celestial  and  terres- 
trial. He  has  worked  diligently  in  the  smelting 
of  ores  as  also  in  the  working  of  minerals  ;  he  is 
thoroughly  acquainted  with  all  sorts  of  arms  and 
implements  used  in  military  service  and  in  hunt- 
ing, besides  which  he  is  skilled  in  agriculture  and 
xii 


INTRODUCTORY 

in  the  measurement  of  lands.  It  is  impossible  to 
write  a  useful  or  correct  treatise  in  experimental 
philosophy  without  mentioning  this  man's  name. 
Moreover,  he  pursues  knowledge  for  its  own  sake; 
for  if  he  wished  to  obtain  royal  favor,  he  could 
easily  find  sovereigns  who  would  honor  and  en- 
rich him." 

This  last  statement  is  worthy  of  the  best  ut- 
terances of  the  twentieth  century.  Say  what  they 
will,  the  most  ardent  pleaders  of  our  day  for  or- 
iginal work  and  laboratory  methods  cannot  sur- 
pass the  Franciscan  monk  of  the  thirteenth  cen- 
tury in  his  denunciation  of  mere  book  learning 
or  in  his  advocacy  of  experiment  and  research, 
while  in  Peregrinus,  the  mediaevalist,  they  have 
Bacon's  impersonation  of  what  a  student  of  sci- 
ence ought  to  be.  Peregrinus  was  a  hard  worker, 
nor  a  mere  theorizer,  preferring,  Procrustean- 
like,  to  make  theory  fit  the  facts  rather  than  facts 
the  theory;  he  was  a  brilliant  discoverer  who 
knew  at  the  same  time  how  to  use  his  discoveries 
for  the  benefit  of  mankind  ;  he  was  a  pioneer  of 
science  and  a  leader  in  the  progress  of  the  world. 


THE   LETTER   OF   PEREGRINUS 

An  analysis  of  the  "  Epistola  "  shows  that 

(a)  Peregrinus  was  the  first  to  assign  a  defi- 
nite position  to  the  poles  of  a  lodestone,  and  to 
give  directions  for  determining  which  is  north  and 
which  south; 

(/£)  He  proved  that  unlike  poles  attract  each 
other,  and  that  similar  ones  repel ; 

(f)  He  established  by  experiment  that  every 
fragment  of  a  lodestone,  however  small,  is  a  com- 
plete magnet,  thus  anticipating  one  of  our  fun- 
damental laboratory  illustrations  of  the  molecu- 
lar theory  ; 

(d)  He  recognized  that  a  pole  of  a  magnet 
may  neutralize  a  weaker  one  of  the  same  name, 
and  even  reverse  its  polarity  ; 

(e)  He  was  the  first  to  pivot  a  magnetized 
needle  and  surround  it  with  a  graduated  circle, 
Figs.  2  and  3.' 

(f )  He  determined  the  position  of  an  object 
by  its  magnetic  bearing  as  done  to-day  in  com- 
pass surveying  ;  and 

1  It  is  probable  that  Flavio  Gioja,  an  Italian  pilot,  some  fifty  years 
later,  added  the  compass-card  and  attached  it  to  the  magnet. 


INTRODUCTORY 

(g)  He  introduced  into  his  perpetual  motion 
machine,  Fig.  4,  the  idea  of  a  magnetic  motor, 
a  clever  idea,  indeed,  for  a  thirteenth  century  en- 
gineer. 

This  rapid  summary  will  serve  to  show  that 
the  letter  of  Peregrinus  is  one  of  great  interest 
in  physics  as  well  as  in  navigation  and  geodesy. 
For  nearly  three  centuries,  it  lay  unnoticed  among 
the  libraries  of  Europe,  but  it  did  not  escape  Gil- 
bert, who  makes  frequent  mention  of  it  in  his 
De  Magnete,  1 600 ;  nor  the  illustrious  Jesuit  writ- 
ers, Cabaeus,  who  refers  to  it  in  his  Pbtlosopbia 
Magnetic  a,  1629,  and  Kircher,  who  quotes  from 
it  in  his  De  Arte  Magnetica,  1641  ;  it  was  well 
known  to  Jean  Taisnier,  the  Belgian  plagiarist, 
who  transferred  a  great  part  of  it  verbatim  to  the 
pages  of  his  De  Natura  Magnetis,  1562,  without 
a  word  of  acknowledgment.  By  this  piece  of 
fraud,  Taisnier  acquired  considerable  celebrity, 
a  fact  that  goes  to  show  the  meritorious  char- 
acter of  the  work  which  he  unscrupulously 
copied. 

This  memorable  letter  is  divided  into  two 


THE   LETTER   OF   PEREGRINUS 

parts  :  the  first  contains  ten  chapters  on  the  gen- 
eral properties  of  the  lodestone ;  the  second  has 
but  three  chapters,  and  shows  how  the  author  pro- 
posed to  use  a  lodestone  for  the  purpose  of  pro- 
ducing continuous  rotation. 

There  are  many  manuscript  copies  of  the  let- 
ter in  European  libraries  :  the  Bodleian  has  six ; 
the  Vatican,  two  ;  Trinity  College,  Dublin,  one; 
the  Bibliotheque  Nationale,  Paris,  one  ;  Leyden, 
Geneva  and  Turin,  one  each.  The  Leyden  MS. 
has  acquired  special  notoriety  from  a  passage  which 
appears  near  the  end  of  it  in  which  reference  is 
made  to  magnetic  declination  and  its  value  given  : 
but  Prof.  W.  Wenckebach,  of  The  Hague,  has 
shown'  that  the  lines  are  spurious,  having  been  in- 
terpolated in  the  manuscript  in  the  early  part  of 
the  sixteenth  century. 

The  Leyden  manuscript  has  also  led  some 
writers  to  believe  in  a  fictitious  author  of  the  let- 
ter, one  Peter  Adsiger,  or  Petrus  Adsigerus.  As 
said  above,  Sigerus  was  the  name  of  his  country- 
man, to  whom  Peregrinus  addressed  his  letter, 

1  Annali  di  Matematica  Pura  ed  Applicata,  1865. 


INTRODUCTORY 

the  Epistola  ad  Sigerum,  from  the  trenches  at  Luc- 
era,  in  August,  1269. 

Magnetic  declination  was  unknown  to  Pere- 
grinus,  else  he  would  not  have  written  the  follow- 
ing words :  "  Wherever  a  man  may  be,  he  finds 
the  lodestone  pointing  to  the  heavens  in  accord- 
ance with  the  position  of  the  meridian  "  (Chapter 
X).  Of  course,  the  geographical  meridian  is  the 
one  here  meant,  as  the  necessity  of  a  distinct 
magnetic  meridian  had  not  yet  occurred  to  any 
one. 

Nor  was  this  important  magnetic  element 
known  to  Columbus  when  he  sailed  from  the 
shores  of  the  Old  World  in  1492  as  appears  from 
the  surprise  with  which  he  noticed  the  deviation 
of  the  needle  from  North  as  well  as  from  the 
consternation  of  his  pilots.  Columbus  has  the 
unquestionable  merit  of  being  the  first  to  observe 
and  record  the  change  of  declination  with  change 
of  place. 

The  first  printed  edition  of  the  Epistola,  now 
very  rare,  was  prepared  by  Achilles  Gasser,  a  phy- 
sician of  Lindau,  a  man  well  versed  in  mathe- 


THE   LETTER   OF   PEREGRINUS 

matics,  astronomy,  history  and  philosophy.  The 
work  was  printed  in  Augsburg  in  1558.  A  copy 
of  this  early  print  is  among  the  treasures  of  the 
Wheeler  collection  in  the  library  of  the  Ameri- 
can Institute  of  Electrical  Engineers,  New  York. 
It  was  from  this  text  that  the  translation  which 
follows  was  made. 

Besides  the  Latin  edition  of  Gasser,  1558, 
there  is  also  that  of  Libri  in  his  Histoire  des  Sci- 
ences Mathematiques,  1838  ;  ofBertelli,  1868,  and 
Hellmann,  1898.  Bertelli's  is  a  learned  and  ex- 
haustive work  in  which  the  Barnabite  monk,  some- 
times called  by  mistake,  Barnabita,  instead  ofBer- 
telli, collates  and  compares  the  readings  of  the 
two  Vatican  codices  with  other  texts,  adding  copi- 
ous references  and  explanatory  notes.  It  appeared 
in  the  Bulletino  di  Bibliografia  e  di  Storia  delle  Scienze 
Matematicbe  e  Fisiche  for  1868. 

Of  translations,  we  have  that  which  Richard 
Eden  made  from  Taisnier's  pirated  extracts,  the 
first  dated  edition  appearing  in  1579.  Cavallo's 
Treatise  on  Magnetism,  1800,  also  contains  some 
of  the  more  remarkable  passages.  The  only  com- 


INTRODUCTORY 

plete  English  translation  that  we  have,  appeared 
in  1902  from  the  scholarly  pen  of  Prof.  Silvanus 
P.  Thompson,  of  London.  It  is  an  edition  deluxe 
beautifully  rubricated,  but  limited  to  250  copies. 
The  translation  was  based  on  the  texts  of  Gasser 
and  Hellmann,  amended  by  reference  to  a  man- 
uscript in  the  author's  possession,  dated  1391. 
We  are  informed  that  Mr.  Fleury  P.  Mottelay, 
of  New  York,  the  learned  translator  of  Gilbert's 
De  Magnete,  possesses  a  manuscript  version  by 
Prof.  Peirce,  of  Harvard,  of  the  Paris  codex,  of 
which  he  made  a  careful  study  in  an  endeavor  to 
decipher  the  illegible  parts. 


PART  I 


THE  LETTER  OF 
PEREGRINUS 


PART   I 

CHAPTER  I 
PURPOSE  OF  THIS  WORK 

DEAREST  OF  FRIENDS: 
T  your  earnest  request,  I  will  now  make 


A 


known  to  you,  in  an  unpolished  narrative, 
the  undoubted  though  hidden  virtue  of  the  lode- 
stone,  concerning  which  philosophers  up  to  the 
present  time  give  us  no  information,  because  it 
is  characteristic  of  good  things  to  be  hidden  in 
darkness  until  they  are  brought  to  light  by  ap- 
plication to  public  utility.  Out  of  affection  for 
you,  I  will  write  in  a  simple  style  about  things 
entirely  unknown  to  the  ordinary  individual. 
Nevertheless  I  will  speak  only  of  the  manifest 
properties  of  the  lodestone,  because  this  tract  will 
form  part  of  a  work  on  the  construction  of  phil- 
osophical instruments.  The  disclosing  of  the 

3 


THE    LETTER    OF   PEREGRINUS 

hidden  properties  of  this  stone  is  like  the  art  of 
the  sculptor  by  which  he  brings  figures  and  seals 
into  existence.  Although  I  may  call  the  matters 
about  which  you  inquire  evident  and  of  inesti- 
mable value,  they  are  considered  by  common 
folk  to  be  illusions  and  mere  creations  of  the  im- 
agination. But  the  things  that  are  hidden  from 
the  multitude  will  become  clear  to  astrologers 
and  students  of  nature,  and  will  constitute  their 
delight,  as  they  will  also  be  of  great  help  to  those 
that  are  old  and  more  learned. 


Y 


CHAPTER    II 
QUALIFICATIONS  OF   THE    EXPERIMENTER 

OU  must  know,  my  dear  friend,  that  who- 


ever wishes  to  experiment,  should  be  ac- 
quainted with  the  nature  of  things,  and  should 
not  be  ignorant  of  the  motion  of  the  celestial 
bodies.  He  must  also  be  skilful  in  manipulation 
in  order  that,  by  means  of  this  stone,  he  may  pro- 
duce these  marvelous  effects.  Through  his  own 
industry  he  can,  to  some  extent,  indeed,  correct 


THE   LETTER    OF   PEREGRINUS 

the  errors  that  a  mathematician  would  inevitably 
make  if  he  were  lacking  in  dexterity.  Besides, 
in  such  occult  experimentation,  great  skill  is  re- 
quired, for  very  frequently  without  it  the  desired 
result  cannot  be  obtained,  because  there  are  many 
things  in  the  domain  of  reason  which  demand 
this  manual  dexterity. 


CHAPTER    III 
CHARACTERISTICS  OF  A   GOOD    LODESTONE 


^TT^HE  lodestone  selected  must  be  distinguished 
-*•  by  four  marks  —  its  color,  homogeneity, 
weight  and  strength.  Its  color  should  be  iron- 
like,  pale,  slightly  bluish  or  indigo,  just  as  pol- 
ished iron  becomes  when  exposed  to  the  corrod- 
ing atmosphere.  I  have  never  yet  seen  a  stone 
of  such  description  which  did  not  produce  won- 
derful effects.  Such  stones  are  found  most  fre- 
quently in  northern  countries,  as  is  attested  by 
sailors  who  frequent  places  on  the  northern  seas, 
notably  in  Normandy,  Flanders  and  Picardy. 
This  stone  should  also  be  of  homogeneous  ma- 


THE    LETTER   OF   PEREGRINUS 

terial ;  one  having  reddish  spots  and  small  holes 
in  it  should  not  be  chosen;  yet  a  lodestone  is 
hardly  ever  found  entirely  free  from  such  blem- 
ishes. On  account  of  uniformity  in  its  compo- 
sition and  the  compactness  of  its  innermost  parts, 
such  a  stone  is  heavy  and  therefore  more  valua- 
ble. Its  strength  is  known  by  its  vigorous  at- 
traction for  a  large  mass  of  iron  ;  further  on  I 
will  explain  the  nature  of  this  attraction.  If  you 
chance  to  see  a  stone  with  all  these  characteris- 
tics, secure  it  if  you  can. 

CHAPTER   IV 

HOW   TO   DISTINGUISH   THE    POLES   OF   A 
LODESTONE 

I  WISH  to  inform  you  that  this  stone  bears  in 
itself  the  likeness  of  the  heavens,  as   I  will 
now  clearly  demonstrate.  There  are  in  the  heav- 
ens two  points  more   important  than  all  others, 
because  on  them,  as  on  pivots,  the  celestial  sphere 
revolves  :   these  points  are  called,  one  the  arctic 
or  north  pole,  the  other  the  antarctic  or  south 
pole.     Similarly  you  must  fully  realize  that  in 
6 


THE    LETTER    OF   PEREGRINUS 

this  stone  there  are  two  points  styled  respect- 
ively the  north  pole  and  the  south  pole.  If  you 
are  very  careful,  you  can  discover  these  two 
points  in  a  general  way.  One  method  for  doing 
so  is  the  following  :  With  an  instrument  with 
which  crystals  and  other  stones  are  rounded  let 
a  lodestone  be  made  into  a  globe  and  then  pol- 
ished. A  needle  or  an  elongated  piece  of  iron 
is  then  placed  on  top  of  the  lodestone  and  a  line 
is  drawn  in  the  direction  of  the  needle  or  iron, 
thus  dividing  the  stone  into  two  equal  parts. 
The  needle  is  next  placed  on  another  part  of  the 
stone  and  a  second  median  line  drawn.  If  de- 
sired, this  operation  may  be  performed  on  many 
different  parts,  and  undoubtedly  all  these  lines 
will  meet  in  two  points  just  as  all  meridian  or 
azimuth  circles  meet  in  the  two  opposite  poles 
of  the  globe.  One  of  these  is  the  north  pole, 
the  other  the  south  pole.  Proof  of  this  will  be 
found  in  a  subsequent  chapter  of  this  tract. 

A  second  method  for  determining  these  im- 
portant points  is  this  :  Note  the  place  on  the 
above-mentioned  spherical  lodestone  where  the 
point  of  the  needle  clings  most  frequently  and 


THE   LETTER   OF   PEREGRINUS 

most  strongly  ;  for  this  will  be  one  of  the  poles 
as  discovered  by  the  previous  method.  In  order 
to  determine  this  point  exactly,  break  off  a  small 
piece  of  the  needle  or  iron  so  as  to  obtain  a  frag- 
ment about  the  length  of  two  fingernails  ;  then 
put  it  on  the  spot  which  was  found  to  be  the 
pole  by  the  former  operation.  If  the  fragment 
stands  perpendicular  to  the  stone,  then  that  is, 
unquestionably,  the  pole  sought  ;  if  not,  then 
move  the  iron  fragment  about  until  it  becomes 
so  ;  mark  this  point  carefully  ;  on  the  opposite 
end  another  point  may  be  found  in  a  similar  man- 
ner. If  all  this  has  been  done  rightly,  and  if 
the  stone  is  homogeneous  throughout  and  a 
choice  specimen,  these  two  points  will  be  dia- 
metrically opposite,  like  the  poles  of  a  sphere. 

CHAPTER   V 

HOW  TO  DISCOVER  THE  POLES  OF  A  LODESTONE  AND 
HOW  TO  TELL  WHICH  IS  NORTH  AND  WHICH  SOUTH 


'T^HE  poles  of  a  lodestone  having  been  located 

-*•        in  a  general  way,  you  will  determine  which 

is  north  and  which  south  in  the  following  man- 

8 


THE   LETTER   OF   PEREGRINUS 

ner  :  Take  a  wooden  vessel  rounded  like  a  plat- 
ter or  dish,  and  in  it  place  the  stone  in  such  a 
way  that  the  two  poles  will  be  equidistant  from 
the  edge  of  the  vessel ;  then  place  the  dish  in 
another  and  larger  vessel  full  of  water,  so  that 
the  stone  in  the  first-mentioned  dish  may  be  like 
a  sailor  in  a  boat.  The  second  vessel  should  be 
of  considerable  size  so  that  the  first  may  resemble 
a  ship  floating  in  a  river  or  on  the  sea.  I  insist 
upon  the  larger  size  of  the  second  vessel  in  order 
that  the  natural  tendency  of  the  lodestone  may 
not  be  impeded  by  contact  of  one  vessel  against 
the  sides  of  the  other.  When  the  stone  has  been 
thus  placed,  it  will  turn  the  dish  round  until  the 
north  pole  lies  in  the  direction  of  the  north  pole 
of  the  heavens,  and  the  south  pole  of  the  stone 
points  to  the  south  pole  of  the  heavens.  Even 
if  the  stone  be  moved  a  thousand  times  away  from 
its  position,  it  will  return  thereto  a  thousand 
times,  as  by  natural  instinct.  Since  the  north 
and  south  parts  of  the  heavens  are  known,  these 
same  points  will  then  be  easily  recognized  in 
the  stone  because  each  part  of  the  lodestone  will 
turn  to  the  corresponding  one  of  the  heavens. 


THE   LETTER   OF   PEREGRINUS 

CHAPTER  VI 
HOW  ONE   LODESTONE   ATTRACTS  ANOTHER 

Til  7HEN  you  have  discovered  the  north  and. 
the  south  pole  in  your  lodestone,  mark 
them  both  carefully,  so  that  by  means  of  these 
indentations  they  may  be  distinguished  whenever 
necessary.  Should  you  wish  to  see  how  one  lode- 
stone  attracts  another,  then,  with  two  lodestones 
selected  and  prepared  as  mentioned  in  the  pre- 
ceding chapter,  proceed  as  follows  :  Place  one 
in  its  dish  that  it  may  float  about  as  a  sailor  in 
a  skiff,  and  let  its  poles  which  have  already  been 
determined  be  equidistant  from  the  horizon,  i.  e., 
from  the  edge  of  the  vessel.  Taking  the  other 
stone  in  your  hand,  approach  its  north  pole  to 
the  south  pole  of  the  lodestone  floating  in  the 
vessel ;  the  latter  will  follow  the  stone  in  your 
hand  as  if  longing  to  cling  to  it.  If,  conversely, 
you  bring  the  south  end  of  the  lodestone  in  your 
hand  toward  the  north  end  of  the  floating  lode- 
stone,  the  same  phenomenon  will  occur  ;  namely, 
the  floating  lodestone  will  follow  the  one  in  your 
hand.  Know  then  that  this  is  the  law  :  the  north 

10 


THE    LETTER   OF   PEREGRINUS 

pole  of  one  lodestone  attracts  the  south  pole  of 
another,  while  the  south  pole  attracts  the  north. 
Should  you  proceed  otherwise  and  bring  the  north 
pole  of  one  near  the  north  pole  of  another,  the 
one  you  hold  in  your  hand  will  seem  to  put  the 
floating  one  to  flight.  If  the  south  pole  of  one 
is  brought  near  the  south  pole  of  another,  the 
same  will  happen.  This  is  because  the  north 
pole  of  one  seeks  the  south  pole  of  the  other, 
and  therefore  repels  the  north  pole.  A  proof  of 
this  is  that  finally  the  north  pole  becomes  united 
with  the  south  pole.  Likewise  if  the  south  pole 
is  stretched  out  towards  the  south  pole  of  the 
floating  lodestone,  you  will  observe  the  latter  to 
be  repelled,  which  does  not  occur,  as  said  before, 
when  the  north  pole  is  extended  towards  the 
south.  Hence  the  silliness  of  certain  persons  is 
manifest,  who  claim  that  just  as  scammony  at- 
tracts jaundice  on  account  of  a  similarity  between 
them,  so  one  lodestone  attracts  another  even  more 
strongly  than  it  does  iron,  a  fact  which  they  sup- 
pose to  be  false  although  really  true  as  shown  by 
experiment. 

ii 


THE   LETTER   OF  PEREGRINUS 

CHAPTER   VII 

HOW     IRON     TOUCHED     BY     A     LODESTONE     TURNS 
TOWARDS    THE    POLES    OF    THE    WORLD 

IT  is  well  known  to  all  who  have  made  the 
experiment,  that  when  an  elongated  piece 
of  iron  has  touched  a  lodestone  and  is  then  fas- 
tened to  a  light  block  of  wood  or  to  a  straw  and 
made  float  on  water,  one  end  will  turn  to  the 
star  which  has  been  called  the  Sailor's  star  be- 
cause it  is  near  the  pole;  the  truth  is,  however, 
that  it  does  not  point  to  the  star  but  to  the  pole 
itself.  A  proof  of  this  will  be  furnished  in  a 
following  chapter.  The  other  end  of  the  iron 
will  point  in  an  opposite  direction.  But  as  to 
which  end  of  the  iron  will  turn  towards  the 
north  and  which  to  the  south,  you  will  observe 
that  that  part  of  the  iron  which  has  touched  the 
south  pole  of  the  lodestone  will  point  to  the  north 
and  conversely,  that  part  which  had  been  in  con- 
tact with  the  north  pole  will  turn  to  the  south. 
Though  this  appears  marvelous  to  the  uniniti- 
ated, yet  it  is  known  with  certainty  to  those  who 
have  tried  the  experiment. 
12 


THE   LETTER   OF   PEREGRINUS 

CHAPTER    VIII 
HOW   A   LODESTONE   ATTRACTS   IRON 

TF  you  wish  the  stone,  according  to  its 'natural 
*•  desire,  to  attract  iron,  proceed  as  follows: 
Mark  the  north  end  of  the  iron  and  towards 
this  end  approach  the  south  pole  of  the  stone, 
when  it  will  be  found  to  follow  the  latter.  Or, 
on  the  contrary,  to  the  south  part  of  the  iron 
present  the  north  pole  of  the  stone  and  the  lat- 
ter will  attract  it  without  any  difficulty.  Should 
you,  however,  do  the  opposite,  namely,  if  you 
bring  the  north  end  of  the  stone  towards  the 
north  pole  of  the  iron,  you  will  notice  the  iron 
turn  round  until  its  south  pole  unites  with  the 
north  end  of  the  lodestone.  The  same  thing 
will  occur  when  the  south  end  of  the  lodestone 
is  brought  near  the  south  pole  of  the  iron. 
Should  force  be  exerted  at  either  pole,  so  that 
when  the  south  pole  of  the  iron  is  made  touch 
the  south  end  of  the  stone,  then  the  virtue  in 
the  iron  will  be  easily  altered  in  such  a  manner 
that  what  was  before  the  south  end  will  now 
become  the  north  and  conversely.  The  cause  is 

13 


THE    LETTER    OF   PEREGRINUS 

that  the  last  impression  acts,  confounds,  or  count- 
eracts and  alters  the  force  of  the  original  move- 
ment. 


CHAPTER    IX 

WHY      THE      NORTH      POLE      OF      ONE      LODESTONE 
ATTRACTS  THE   SOUTH    POLE   OF  AN- 
OTHER AND  VICE  VERSA 

\  S  already  stated,  the  north  pole  of  one  lode- 
•*•  ^-  stone  attracts  the  south  pole  of  another 
and  conversely;  in  this  case  the  virtue  of  the 
stronger  becomes  active,  whilst  that  of  the  weaker 
becomes  obedient  or  passive.  I  consider  the  fol- 
lowing to  be  the  cause  of  this  phenomenon :  the 
active  agent  requires  a  passive  subject,  not  merely 
to  be  joined  to  it,  but  also  to  be  united  with  it, 
so  that  the  two  make  but  one  by  nature.  In  the 
case  of  this  wonderful  lodestone  this  may  be 
shown  in  the  following  manner:  Take  a  lode- 
stone  which  you  may  call  A  Z),  in  which  A  is 
the  north  pole  and  D  the  south  ;  cut  this  stone 
into  two  parts,  so  that  you  may  have  two  distinct 

14 


THE    LETTER   OF   PEREGRINUS 

stones ;  place  the  stone  having  the  pole  A  so 
that  it  may  float  on  water  and  you  will  observe 
that  A  turns  towards  the  north  as  before;  the 
breaking  did  not  destroy  the  properties  of  the 
parts  of  the  stone,  since  it  is  homogeneous; 
hence  it  follows  that  the  part  of  the  stone  at 
the  point  of  fracture,  which  may  be  marked  By 
must  be  a  south  pole;  this  broken  part  of  which 
we  are  now  speaking  may  be  called  A  B.  The 
other,  which  contains  D,  should  then  be  placed 
so  as  to  float  on  water,  when  you  will  see  D 
point  towards  the  south  because  it  is  a  south 
pole ;  but  the  other  end  at  the  point  of  fracture, 
lettered  C,  will  be  a  north  pole;  this  stone  may 
now  be  named  C  D.  If  we  consider  the  first 
stone  as  the  active  agent,  then  the  second,  or 
C  D,  will  be  the  passive  subject.  You  will  also 
notice  that  the  ends  of  the  two  stones  which 
before  their  separation  were  together,  after 
breaking  will  become  one  a  north  pole  and  the 
other  a  south  pole.  If  now  these  same  broken 
portions  are  brought  near  each  other,  one  will 
attract  the  other,  so  that  they  will  again  be 

15 


THE   LETTER   OF   PEREGRINUS 

joined  at  the  points  B  and  C,  where  the  fracture 
occurred.  Thus,  by  natural  instinct,  one  single 
stone  will  be  formed  as  before.  This  may  be 
demonstrated  fully  by  cementing  the  parts  to- 
gether, when  the  same  effects  will  be  produced 
as  before  the  stone  was  broken.  As  you  will 
perceive  from  this  experiment,  the  active  agent 
desires  to  become  one  with  the  passive  subject 
because  of  the  similarity  that  exists  between 
them.  Hence  C,  being  a  north  pole,  must  be 
brought  close  to  j£,  so  that  the  agent  and  its 
subject  may  form  one  and  the  same  straight  line 
in  the  order  A  B,  C  D  and  B  and  C  being  at 
the  same  point.  In  this  union  the  identity 
of  the  extreme  parts  is  retained  and  preserved 
just  as  they  were  at  first;  for  A  is  the  north  pole 
in  the  entire  line  as  it  was  in  the  divided  one; 
so  also  D  is  the  south  pole  as  it  was  in  the  di- 
vided passive  subject,  but  B  and  C  have  been 
made  effectually  into  one.  In  the  same  way  it 
happens  that  if  A  be  joined  to  D  so  as  to  make 
the  two  lines  one,  in  virtue  of  this  union  due  to 
attraction  in  the  order  C  D  A  B,  then  A  and  D 
16 


THE   LETTER   OF   PEREGRINUS 

will  constitute  but  one  point,  the  identity  of  the 
extreme  parts  will  remain  unchanged  just  as  they 
were  before  being  brought  together,  for  C  is  a 
north  pole  and  B  a  south,  as  during  their  sepa- 
ration. If  you  proceed  in  a  different  fashion, 
this  identity  or  similarity  of  parts  will  not  be 
preserved ;  for  you  will  perceive  that  if  C,  a 
north  pole,  be  joined  to  A,  a  north  pole,  con- 
trary to  the  demonstrated  truth,  and  from  these 
two  lines  a  single  one,  B  A  C  £),  is  formed,  as 
D  was  a  south  pole  before  the  parts  were  united, 
it  is  then  necessary  that  the  other  extremity 
should  be  a  north  pole,  and  as  B  is  a  south  pole, 
the  identity  of  the  parts  of  the  former  similarity 
is  destroyed.  If  you  make  B  the  south  pole  as 
it  was  before  they  united,  then  D  must  become 
north,  though  it  was  south  in  the  original  stone ; 
in  this  way  neither  the  identity  nor  similarity 
of  parts  is  preserved.  It  is  becoming  that  when 
the  two  are  united  into  one,  they  should  bear 
the  same  likeness  as  the  agent,  otherwise  nature 
would  be  called  upon  to  do  what  is  impossible. 
The  same  incongruity  would  occur  if  you  were 


THE   LETTER   OF  PEREGRINUS 

to  join  B  with  D  so  as  to  make  the  line  A  B  D  C, 
as  is  plain  to  any  person  who  reflects  a  moment. 
Nature,  therefore,  aims  at  being  and  also  at  act- 
ing in  the  best  manner  possible  ;  it  selects  the 
former  motion  and  order  rather  than  the  second 
because  the  identity  is  better  preserved.  From 
all  this  it  is  evident  why  the  north  pole  attracts 
the  south  and  conversely,  and  also  why  the  south 
pole  does  not  attract  the  south  pole  and  the 
north  pole  does  not  attract  the  north. 

CHAPTER  x 

AN    INQUIRY    INTO    THE    CAUSE   OF  THE    NATURAL 
VIRTUE    OF    THE     LODESTONE 


persons  who  were  but  poor  in- 
vestigators  of  nature  held  the  opinion  that 
the  force  with  which  a  lodestone  draws  iron,  is 
found  in  the  mineral  veins  themselves  from  which 
the  stone  is  obtained  ;  whence  they  claim  that 
the  iron  turns  towards  the  poles  of  the  earth,  only 
because  of  the  numerous  iron  mines  found  there. 
But  such  persons  are  ignorant  of  the  fact  that  in 
18 


THE    LETTER   OF   PEREGRINUS 

many  different  parts  of  the  globe  the  lodestone 
is  found;  from  which  it  would  follow  that  the  iron 
needle  should  turn  in  different  directions  accord- 
ing to  the  locality  ;  but  this  is  contrary  to  expe- 
rience. Secondly,  these  individuals  do  not  seem  to 
know  that  the  places  under  the  poles  are  unin- 
habitable because  there  one-half  the  year  is  day 
and  the  other  half  night.  Hence  it  is  most  silly 
to  imagine  that  the  lodestone  should  come  to  us 
from  such  places.  Since  the  lodestone  points  to  the 
south  as  well  as  to  the  north,  it  is  evident  from 
the  foregoing  chapters  that  we  must  conclude 
that  not  only  from  the  north  pole  but  also  from 
the  south  pole  rather  than  from  the  veins  of  the 
mines  virtue  flows  into  the  poles  of  the  lodestone. 
This  follows  from  the  consideration  that  wher- 
ever a  man  may  be,  he  finds  the  stone  pointing 
to  the  heavens  in  accordance  with  the  position 
of  the  meridian;  but  all  meridians  meet  in  the 
poles  of  the  world ;  hence  it  is  manifest  that 
from  the  poles  of  the  world,  the  poles  of  the 
lodestone  receive  their  virtue.  Another  neces- 
sary consequence  of  this  is  that  the  needle  does 

19 


THE   LETTER    OF   PEREGRINUS 

not  point  to  the  pole  star,  since  the  meridians 
do  not  intersect  in  that  star  but  in  the  poles  of 
the  world.  In  every  region,  the  pole  star  is  al- 
ways found  outside  the  meridian  except  twice  in 
each  complete  revolution  of  the  heavens.  From 
all  these  considerations,  it  is  clear  that  the  poles 
of  the  lodestone  derive  their  virtue  from  the 
poles  of  the  heavens.  As  regards  the  other  parts 
of  the  stone,  the  right  conclusion  is,  that  they 
obtain  their  virtue  from  the  other  parts  of  the 
heavens,  so  that  we  may  infer  that  not  only 
the  poles  of  the  stone  receive  their  virtue  and 
influence  from  the  poles  of  the  world,  but  like- 
wise also  the  other  parts,  or  the  entire  stone  from 
the  entire  heavens.  You  may  test  this  in  the 
following  manner  :  A  round  lodestone  on  which 
the  poles  are  marked  is  placed  on  two  sharp  styles 
as  pivots  having  one  pivot  under  each  pole  so 
that  the  lodestone  may  easily  revolve  on  these 
pivots.  Having  done  this,  make  sure  that  it  is 
equally  balanced  and  that  it  turns  smoothly  on 
the  pivots.  Repeat  this  several  times  at  different 
hours  of  the  day  and  always  with  the  utmost 


THE   LETTER   OF   PEREGRINUS 

care.  Then  place  the  stone  with  its  axis  in 
the  meridian,  the  poles  resting  on  the  pivots. 
Let  it  be  moved  after  the  manner  of  bracelets  so 
that  the  elevation  and  depression  of  the  poles  may 
equal  the  elevation  and  depressions  of  the  poles 
of  the  heavens  of  the  place  in  which  you  are  ex- 
perimenting. If  now  the  stone  be  moved  ac- 
cording to  the  motion  of  the  heavens,  you  will 
be  delighted  in  having  discovered  such  a  won- 
derful secret ;  but  if  not,  ascribe  the  failure  to 
your  own  lack  of  skill  rather  than  to  a  defect  in 
nature.  Moreover,  in  this  position  I  consider 
the  strength  of  the  lodestone  to  be  best  preserved. 
When  it  is  placed  differently,  i.  e.,  not  in  the  mer- 
idian, I  think  its  virtue  is  weakened  or  obscured 
rather  than  maintained.  With  such  an  instrument 
you  will  need  no  timepiece,  for  by  it  you  can  know 
the  ascendant  at  any  hour  you  please,  as  well  as 
all  other  dispositions  of  the  heavens  which  are 
sought  for  by  astrologers. 


21 


PART  II 


THE  LETTER  OF 
PEREGRINUS 


PART   II 

CHAPTER   I 

THE  CONSTRUCTION  OF  AN  INSTRUMENT  FOR  MEAS- 
URING    THE     AZIMUTH      OF     THE      SUN 
THE     MOON      OR     ANY     STAR 
ON    THE     HORIZON 

HAVING  fully  examined  all  the  properties 
of  the  lodestone  and  the  phenomena  con- 
nected therewith,  let  us  now  come  to  those  in- 
struments which  depend  for  their  operation  on 
the  knowledge  of  those  facts.  Take  a  rounded 
lodestone,1  and  after  determining  its  poles  in  the 
manner  already  mentioned,  file  its  two  sides  so 
that  it  becomes  elongated  at  its  poles  and  occu- 
pies less  space.  The  lodestone  prepared  in  this 
wise  is  then  enclosed  within  two  capsules  after 
the  fashion  of  a  mirror.  Let  these  capsules  be 
so  joined  together  that  they  cannot  be  sepa- 

1 A  terrella,  or  earthkin. 

25 


THE    LETTER   OF   PEREGRINUS 

rated  and  that  water  cannot  enter ;  they  should 
be  made  of  light  wood  and  fastened  with  cement 
suited  to  the  purpose.  Having  done  this,  place 
them  in  a  large  vessel  of  water  on  the  edges  of 
which  the  two  parts  of  the  world,  i.  e.,  the 
north  and  south  points,  have  been  found  and 
marked.  These  points  may  be  united  by  a 
thread  stretched  across  from  north  to  south. 
Then  float  the  capsules  and  place  a  smooth  strip 
of  wood  over  them  in  the  manner  of  a  diam- 
eter. Move  the  strip  until  it  is  equally  distant 
from  the  meridian-line,  previously  determined 
and  marked  by  a  thread,  or  else  until  it  coin- 
cides therewith.  Then  mark  a  line  on  the  cap- 
sules according  to  the  position  of  the  strip,  and 
this  will  indicate  forever  the  meridian  of  that 
place.  Let  this  line  be  divided  at  its  middle  by 
another  cutting  it  at  right  angles,  which  will 
give  the  east  and  west  line  ;  thus  the  four  cardi- 
nal points  will  be  determined  and  indicated  on 
the  edge  of  the  capsules.  Each  quarter  is  to  be 
subdivided  into  90  parts,  making  360  in  the  cir- 
cumference of  the  capsules.  Engrave  these  divi- 
26 


THE    LETTER    OF   PEREGRINUS 

sions  on  them  as  usually  done  on  the  back  of 
an  astrolabe.  On  the  top  or  edge  of  the  cap- 
sules thus  marked  place  a  thin  ruler  like  the 
pointer  on  the  back  of  the  astrolabe  ;  instead  of 
the  sights  attach  two  perpendicular  pins,  one  at 
each  end.  If,  therefore,  you  desire  to  take  the 
azimuth  of  the  sun,  place  the  capsules  in  water 
and  let  them  move  freely  until  they  come  to 
rest  in  their  natural  position.  Hold  them  firmly 
in  one  hand,  while  with  the  other  you  move  the 
ruler  until  the  shadow  of  the  pins  falls  along  the 
length  of  the  ruler ;  then  the  end  of  the  ruler 
which  is  towards  the  sun  will  indicate  the  azi- 
muth of  the  sun.  Should  it  be  windy,  let  the 
capsules  be  covered  with  a  suitable  vessel  until 
they  have  taken  their  position  north  and  south. 
The  same  method,  namely,  by  sighting,  may  be 
followed  at  night  for  determining  the  azimuth 
of  the  moon  and  stars ;  move  the  ruler  until  the 
ends  of  the  pins  are  in  the  same  line  with  the 
moon  or  star ;  the  end  of  the  ruler  will  then  in- 
dicate the  azimuth  just  as  in  the  case  of  the  sun. 
By  means  of  the  azimuth  may  then  be  deter- 

27 


THE   LETTER   OF   PEREGRINUS 

mined  the  hour  of  the  day,  the  ascendant,  and 
all  those  other  things  usually  determined  by  the 
astrolabe.  A  form  of  the  instrument  is  shown 
in  the  following  figure. 


FIG.  I. — AZIMUTH   COMPASS 

CHAPTER    II 

THE   CONSTRUCTION    OF   A    BETTER     INSTRUMENT 
FOR   THE   SAME   PURPOSE 

TN  this  chapter  I  will  describe  the  construc- 
-*"  tion  of  a  better  and  more  efficient  instrument. 
Select  a  vessel  of  wood,  brass  or  any  solid  ma- 
terial you  like,  circular  in  shape,  moderate  in 
28 


THE   LETTER   OF   PEREGRINUS 

size,  shallow  but  of  sufficient  width,  with  a  cover 
of  some  transparent  substance,  such  as  glass  or 
crystal;  it  would  be  even  better  to  have  both 
the  vessel  and  the  cover  transparent.  At  the 
centre  of  this  vessel  fasten  a  thin  axis  of  brass 
or  silver,  having  its  extremities  in  the  cover 
above  and  the  vessel  below.  At  the  middle  of 
this  axis  let  there  be  two  apertures  at  right  an- 
gles to  each  other ;  through  one  of  them  pass 
an  iron  stylus  or  needle,  through  the  other  a  sil- 
ver or  brass  needle  crossing  the  iron  one  at  right 
angles.  Divide  the  cover  first  into  four  parts 
and  subdivide  these  into  90  parts,  as  was  men- 
tioned in  describing  the  former  instrument. 
Mark  the  parts  north,  south,  east  and  west.  Add 
thereto  a  ruler  of  transparent  material  with  pins 
at  each  end.  After  this  bring  either  the  north 
or  the  south  pole  of  a  lodestone  near  the  cover 
so  that  the  needle  may  be  attracted  and  receive 
its  virtue  from  the  lodestone.  Then  turn  the 
vessel  until  the  needle  stands  in  the  north  and 
south  line  already  marked  on  the  instrument ; 
after  which  turn  the  ruler  towards  the  sun  if 
29 


THE   LETTER    OF   PEREGRINUS 

day-time,  and  towards  the  moon  and  stars  at 
night,  as  described  in  the  preceding  chapter. 
By  means  of  this  instrument  you  can  direct  your 
course  towards  cities  and  islands  and  any  other 


FIG.  2. — DOUBLE-PIVOTED  NEEDLE 


FIG.  3. — PIVOTED  COMPASS 


place  wherever  you  may  wish  to  go  by  land  or 
sea,  provided  the  latitude  and  longitude  of  the 
places  are  known  to  you.  How  iron  remains 
suspended  in  air  by  virtue  of  the  lodestone,  I 
will  explain  in  my  book  on  the  action  of  mir- 

30 


THE    LETTER   OF   PEREGRINUS 

rors.    Such,  then,  is  the  description  of  the  instru- 
ment illustrated  below.      (See  Figs.  2  and  3.) 


CHAPTER    III 

THE     ART     OF     MAKING    A    WHEEL    OF 
PERPETUAL    MOTION 

IN  this  chapter  I  will  make  known  to  you  the 
construction  of  a  wheel  which  in  a  remark- 
able manner  moves  continuously.  I  have  seen 
many  persons  vainly  busy  themselves  and  even 
becoming  exhausted  with  much  labor  in  their 
endeavors  to  invent  such  a  wheel.  But  these  in- 
variably failed  to  notice  that  by  means  of  the  vir- 
tue or  power  of  the  lodestone  all  difficulty  can  be 
overcome.  For  the  construction  of  such  a  wheel, 
take  a  silver  capsule  like  that  of  a  concave  mir- 
ror, and  worked  on  the  outside  with  fine  carv- 
ing and  perforations,  not  only  for  the  sake  of 
beauty,  but  also  for  the  purpose  of  diminishing 
its  weight.  You  should  manage  also  that  the 
eye  of  the  unskilled  may  not  perceive  what  is 
cunningly  placed  inside.  Within  let  there  be 


THE    LETTER   OF   PEREGRINUS 

iron  nails  or  teeth  of  equal  weight  fastened  to 
the  periphery  of  the  wheel  in  a  slanting  direc- 
tion, close  to  one  another  so  that  their  distance 
apart  may  not  be  more  than  the  thickness  of  a 
bean  or  a  pea  ;  the  wheel  itself  must  be  of  uni- 
form weight  throughout.  Fasten  the  middle  of 
the  axis  about  which  the  wheel  revolves  so  that 
the  said  axis  may  always  remain  immovable.  Add 
thereto  a  silver  bar,  and  at  its  extremity  affix  a 
lodestone  placed  between  two  capsules  and  pre- 
pared in  the  following  way  :  When  it  has  been 
rounded  and  its  poles  marked  as  said  before,  let 
it  be  shaped  like  an  egg  ;  leaving  the  poles  un- 
touched, file  down  the  intervening  parts  so  that 
thus  flattened  and  occupying  less  space,  it  may 
not  touch  the  sides  of  the  capsules  when  the 
wheel  revolves.  Thus  prepared,  let  it  be  attached 
to  the  silver  rod  just  as  a  precious  stone  is  placed 
in  a  ring  ;  let  the  north  pole  be  then  turned  to- 
wards the  teeth  or  cogs  of  the  wheel  somewhat 
slantingly  so  that  the  virtue  of  the  stone  may  not 
flow  diametrically  into  the  iron  teeth,  but  at  a 
certain  angle  ;  consequently  when  one  of  the 

32 


THE   LETTER   OF   PEREGRINUS 

teeth  comes  near  the  north  pole  and  owing  to 
the  impetus  of  the  wheel  passes  it,  it  then  ap- 
proaches the  south  pole  from  which  it  is  rather 
driven  away  than  attracted,  as  is  evident  from  the 
law  given  in  a  preceding  chapter.  Therefore  such 
a  tooth  would  be  constantly  attracted  and  con- 


FIG.  4.— PERPETUAL   MOTION  WHEEL 


stantly  repelled.  In  order  that  the  wheel  may 
do  its  work  more  speedily,  place  within  the  box  a 
small  rounded  weight  made  of  brass  or  silver  of 
such  a  size  that  it  may  be  caught  between  each 
pair  of  teeth ;  consequently  as  the  movement  of 

33 


THE    LETTER   OF   PEREGRINUS 

the  wheel  is  continuous  in  one  direction,  so  the 
fall  of  the  weight  will  be  continuous  in  the  other. 
Being  caught  between  the  teeth  of  a  wheel  which 
is  continuously  revolving,  it  seeks  the  centre  of  the 
earth  in  virtue  of  its  own  weight,  thereby  aiding 
the  motion  of  the  teeth  and  preventing  them  from 
coming  to  rest  in  a  direct  line  with  the  lode- 
stone.  Let  the  places  between  the  teeth  be  suit- 
ably hollowed  out  so  that  they  may  easily  catch 
the  body  in  its  fall,  as  shown  in  the  diagram 
above.  (Fig.  4.) 

Farewell :  finished  in  camp  at  the  siege  of 
Lucera  on  the  eighth  day  of  August,  Anno  Dom- 
ini MCCLXIX. 


34 


NOTES 


35 


EARLY     REFERENCES    TO 
THE  MARINER'S  COMPASS 


THE  following  are  the  passages  referred  to  in  the  intro- 
ductory notice: 

Abbot  Neckam  (1157-1217),  in  his  De  Naturis  Rerum, 
writes : 

"The  sailors,  moreover,  as  they  sail  over  the  sea,  when  in 
cloudy  weather  they  can  no  longer  profit  by  the  light  of  the  sun, 
or  when  the  world  is  wrapped  up  in  the  darkness  of  the  shades 
of  night  and  they  are  ignorant  to  what  point  their  ship's  course 
is  directed,  these  mariners  touch  the  lodestone  with  a  needle, 
which  (the  needle)  is  whirled  round  in  a  circle  until  when  its 
motion  ceases,  its  point  looks  direct  to  the  north.  (Cuspis 
ipsius  septentrionalem  plagam  respiciat.)" 

In  his  De  Utensilibus,  we  read : 

"Among  other  stores  of  a  ship,  there  must  be  a  needle 
mounted  on  a  dart  (habeat  etiam  acum  jaculo  superpositam] 
which  will  oscillate  and  turn  until  the  point  looks  to  the  north, 
and  the  sailors  will  thus  know  how  to  direct  their  course  when 

37 


THE    LETTER   OF   PEREGRINUS 

the  pole  star  is  concealed  through  the  troubled  state  of  the  at- 
mosphere." 1 

Alexander  Neckam  was  born  at  St.  Albans  in  1157,  joined 
the  Augustinian  Order  and  taught  in  the  University  of  Paris 
from  1180  to  1187,  after  which  he  returned  to  England  to  take 
charge  of  a  College  of  his  Order  at  Dunstable.  He  was  elected 
Abbot  of  Cirencester  in  1213  and  died  at  Kemsey,  near  Wor- 
cester, in  1217. 

The  satirical  poem  of  Guyot  de  Provins,  written  about 
1208,  contains  the  following  passage: 

The  mariners  employ  an  art  which  cannot  deceive, 

By  the  property  of  the  lodestone, 

An  ugly  stone  and  brown, 

To  which  iron  joints  itself  willingly 

They  have;  they  attend  to  where  it  points 

After  they  have  applied  a  needle  to  it  j 

And  they  lay  the  latter  on  a  straw 

And  put  it  simply  in  the  water 

Where  the  straw  makes  it  float. 

Then  the  point  turns  direct 

To  the  star  with  such  certainty 

That  no  man  will  ever  doubt  it, 

Nor  will  it  ever  go  wrong. 

When  the  sea  is  dark  and  hazy, 

That  one  sees  neither  star  nor  moon, 

Then  they  put  a  light  by  the  needle 

And  have  no  fear  of  losing  their  way. 

The  point  turns  towards  the  star ; 

*The  Chronicles  and  Memoirs  of  Great  Britain  and  Ireland  during 
the  Middle  Ages,  by  Thomas  Wright  (1863). 

38 


NOTES 

And  the  mariners  are  taught 
To  follow  the  right  way. 
It  is  an  art  which  cannot  fail. 


Provins,  from  wKich  Guyot  took  his  surname,  was  a  small 
town  in  the  vicinity  of  Paris. 

Cardinal  Jacques  de  Vitry,  in  his  Htstoria  Orientalis,  Cap. 
89,  writes: 

"An  iron  needle,  after  having  been  in  contact  with  the 
lodestone,  turns  towards  the  north  star,  so  that  it  is  very  neces- 
sary for  those  who  navigate  the  seas." 

Jacques  de  Vitry  was  born  at  Argenteuil,  near  Paris,  joined 
the  fourth  crusade,  became  Bishop  of  Ptolemais,  and  died  in 
Rome  in  1244.  He  wrote  his  "Description  of  Palestine," 
which  forms  the  first  book  of  his  Historia  Orientalis,  in  the 
East,  between  1215  and  1220. 

Albertus  Magnus  (1193-1280)  in  his  De  Mineralibus,  Lib. 
II.,  Tract  3,  Cap.  6,  writes: 

"It  is  the  end  of  the  lodestone  which  makes  the  iron  that 
touched  it  turn  to  the  north  (ad  zoron)  and  which  is  of  use  to 
mariners;  but  the  other  end  of  the  needle  turns  toward  the 
south  (ad  apkron)" 

This  illustrious  Bavarian  schoolman  joined  the  Dominican 
Order  in  his  youth,  lectured  to  great  audiences  in  Cologne,  be- 
came bishop  of  Ratisbonne  in  1260,  and  died  in  1280.  Thomas 
Aquinas  the  greatest  of  schoolmen,  was  among  his  pupils. 

39 


THE    LETTER    OF   PEREGRINUS 

In  the  Spanish  code  of  laws,  begun  in  1256,  during  the 
reign  of  Alfonso  el  Sabio,  and  known  as  Las  Siete  Partidas,  we 
read: 

"Just  as  mariners  are  guided  during  the  night  by  the 
needle,  which  replaces  for  them  the  shores  and  pole  star  alike, 
by  showing  them  the  course  to  pursue  both  in  fair  weather  and 
foul,  so  those  who  are  called  upon  to  advise  the  King  must  al- 
ways be  guided  by  a  spirit  of  justice." 

Brunette  Latini,  in  his  Tresor  des  Sciences,  1260,  writes: 

"The  sailors  navigate  the  seas  guided  by  the  two  stars 
called  the  tramontanes,  and  each  of  the  two  parts  of  the  lode- 
stone  directs  the  end  of  the  needle  to  the  star  to  which  that  part 
itself  turns." 

Brunette  Latini  (1230-1294)  was  a  man  of  great  eminence 
in  the  thirteenth  century;  Dante  was  among  his  pupils  at  Flor- 
ence. For  political  reasons,  he  removed  to  Paris,  where  he 
wrote  his  Tresor  and  also  his  Tesoretto.  He  visited  Roger 
Bacon  at  Oxford  about  1260. 

In  his  treatise  De  Contemplatione,  begun  in  1272,  Ray- 
mond Lully  writes : 

"As  the  needle,  after  having  touched  the  lodestone,  turns 
to  the  north,  so  the  mariner's  needle  (acus  nautica)  directs  them 
over  the  sea." 

Lully  was  born  at  Palma  in  the  Island  of  Majorca  in 
1236;  he  joined  the  Third  Order  of  St.  Francis,  dying  in  1315. 

40 


NOTES 

Ristoro  d'Arezzo,  in  his  Libra  della  Composizione  del 
Mundo,  written  in  1282,  has  the  following: 

"  Besides  this,  there  is  the  needle  which  guides  the  mariner, 
and  which  is  itself  directed  by  the  star  called  the  tramontane."  x 

The  following  metrical  translation  of  a  poem  by  Guido 
Guinicelli,  an  Italian  priest,  1276,  is  from  the  pen  of  Dr.  Park 
Benjamin,  of  New  York: 

In  what  strange  regions  'neath  the  polar  star 
May  the  great  hills  of  massy  lodestone  rise, 
Virtue  imparting  to  the  ambient  air 
To  draw  the  stubborn  iron  ;  while  afar 
From  that  same  stone,  the  hidden  virtue  flies 
To  turn  the  quivering  needle  to  the  Bear 
In  splendor  blazing  in  the  Northern  skies. 

The  above  extracts  show  that  the  directive  property  of  the 
magnetic  needle  was  well  known  in  England,  France,  Germany, 
Spain  and  Italy  in  the  thirteenth  century.  In  the  passage  from 
Neckam,  the  acum  jaculo  superposltam  has  been  construed  by 
some  to  mean  a  form  of  pivoted  needle,  while  in  the  letter  of 
Peregrinus,  1269,  the  double  pivoted  form  is  clearly  described. 


1  The  pole-star  was  thus  named  in  the  south  of  France  and  the  north 
of  Italy  because  seen  beyond  the  mountains  (the  Alps). 

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